I guess I posted on this thread, didn't mean to.

I'm pretty sure it wasn't fermenting any more. It might have warmed
up a few degrees. There must have been a hidden flaw. I've had
demijohns with solid bungs outside to cold stabilize them without
problem.

Demijohns actually have pretty thin glass compared to bottles. One of
my demijohns is green glass. When I filled with with fermenting
Sauvignon Blanc wine, there was a thin spot on the glass that became
readily apparent with the brown wine in it. It is scary actually now
that I broke one.



(pp) wrote in message . com>...
> (Dan Emerson) wrote in message . com>...
> > Well I certainly learned a lesson today.
> >
> > I had a cabernet all finished sitting in a demijohn, just waiting a
> > bit to age and bottle. From last years harvest from Lanza Ranch. I
> > had put it in a room with some Sauvignon Blanc that is just finishing
> > fermentation, so I was keeping the room cool, about 50 degrees. The
> > air lock on the cabernet kept draining into the wine as it changed
> > volume due to changing temperature. So I put a bung in it. Good and
> > tight.
> >
> > Today my wife calls me at work to say that there is cabernet all over
> > the floor! The demijohn cracked, apparently due to pressure due to
> > temperature changes. 54 liters of fine wine all over the carpet. The
> > carpet was crap and due to be tossed anyway.
> >
> > Should a demijohn be able to take the small stresses from temperature
> > changes when it is bunged tight? Seems weak to me. Anybody else
> > experience this?
> >
> > I'm bummed.
> >
> > Dan
>
> Not that it changes anything, but it's quite possible the demijohn
> exploded because the wine was expanding rather than contracting. If
> your romm was set at constant 50, the Cab would go to that level in 1
> day, 2 at most. So after that it wouldn't have any reason to contract
> further. It sounds from your description that you had airlock on for a
> while before the solid bung. So it's possible the Cab was still
> fermenting and the generated CO2 pressure exploded the carboy.
>
> I can't say about demijohns, but I routinely move carboys with a solid
> bung into a fridge for cold stabilization. I've also heard of people
> using a vacuum pump on carboys to degass without breakage. But yeah,
> the glass on demijohns looks pretty fragile to me, so I can see how
> there could be a problem, especially it there was a hidden fault in
> the glass.
>
> Pp